https://llvm.org/bugs/show_bug.cgi?id=31606
Bug ID: 31606
Summary: regression, using parent constructor enables illegal
implicit casts
Product: clang
Version: 3.9
Hardware: PC
OS: FreeBSD
Status: NEW
Severity: normal
Priority: P
Component: C++
Assignee: unassignedclangb...@nondot.org
Reporter: kamik...@bsdforen.de
CC: dgre...@apple.com, llvm-bugs@lists.llvm.org
Classification: Unclassified
Created attachment 17829
--> https://llvm.org/bugs/attachment.cgi?id=17829&action=edit
Minimal testcase
For context, here is the attached test case:
~~~
struct Base {};
struct A : Base {
using Base::Base;
bool operator ==(A const&) const;
};
struct B : Base {
using Base::Base;
};
bool foo() {
return A{} == A{} &&
A{} == B{};
}
~~~
The provided test case compiles with clang++39:
~~~
# clang++39 -std=c++11 -c test.cpp -o test.o
#
~~~
I expect it to fail, e.g. with clang++38:
~~~
# clang++38 -std=c++11 -c test.cpp -o test.o
test.cpp:14:13: error: invalid operands to binary expression ('A' and 'B')
A{} == B{};
~~~ ^ ~~~
test.cpp:5:7: note: candidate function not viable: no known conversion from 'B'
to 'const A' for 1st argument
bool operator ==(A const&) const;
^
1 error generated.
#
~~~
Or GCC:
~~~
# g++5 -std=c++11 -c test.cpp -o test.o
test.cpp: In function 'bool foo()':
test.cpp:14:13: error: no match for 'operator==' (operand types are 'A' and
'B')
A{} == B{};
^
test.cpp:5:7: note: candidate: bool A::operator==(const A&) const
bool operator ==(A const&) const;
^
test.cpp:5:7: note: no known conversion for argument 1 from 'B' to 'const A&'
#
~~~
This triggers some static_asserts() with SFINAE tests in one of my projects, it
took me a while to decouple the problem from all the template-fu.
Here is the relevant system info:
# uname -a
FreeBSD AprilRyan.norad 11.0-STABLE FreeBSD 11.0-STABLE #0 r311880: Tue Jan 10
22:24:08 CET 2017 root@AprilRyan.norad:/usr/obj/S403/amd64/usr/src/sys/S403
amd64
# clang++39 -v
clang version 3.9.1 (tags/RELEASE_391/final)
Target: x86_64-unknown-freebsd11.0
Thread model: posix
InstalledDir: /usr/local/llvm39/bin
# clang++38 -v
clang version 3.8.1 (tags/RELEASE_381/final)
Target: x86_64-unknown-freebsd11.0
Thread model: posix
InstalledDir: /usr/local/llvm38/bin
# g++5 -v
Using built-in specs.
COLLECT_GCC=g++5
COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc5/gcc/x86_64-portbld-freebsd11.0/5.4.0/lto-wrapper
Target: x86_64-portbld-freebsd11.0
Configured with: /tmp/obj/usr/ports/lang/gcc5/work/gcc-5.4.0/configure
--disable-bootstrap --disable-nls --enable-gnu-indirect-function
--libdir=/usr/local/lib/gcc5 --libexecdir=/usr/local/libexec/gcc5
--program-suffix=5 --with-as=/usr/local/bin/as --with-gmp=/usr/local
--with-gxx-include-dir=/usr/local/lib/gcc5/include/c++/
--with-ld=/usr/local/bin/ld --with-pkgversion='FreeBSD Ports Collection'
--with-system-zlib --disable-libgcj --enable-languages=c,c++,objc,fortran
--prefix=/usr/local --localstatedir=/var --mandir=/usr/local/man
--infodir=/usr/local/info/gcc5 --build=x86_64-portbld-freebsd11.0
Thread model: posix
gcc version 5.4.0 (FreeBSD Ports Collection)
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